In a few instances, researchers have found that synthetic peptides act as immunogens to provide protection against viruses. To function in this manner, a peptide must be coupled to a carrier protein in order to remain in the host long enough for an immune response. Attempts are underway to improve the peptide to carrier protein conjugation strategy by developing vaccines composed of peptide polymers without protein. Such vaccines of highly defined chemical composition may be specific for a certain pathogen, without the side effects that often occur in the peptide-carrier protein approach. New methods for conjugation and methods to evaluate the degree of conjugation are being developed in this laboratory. Such methods will be useful in the quality control of peptide polymers and are needed to define the reproducibility of the syntheses. A compound, N-alpha-tBOC-xi-bromoacetyl-B-alanyl-L-lysine, prepared in this laboratory is designed to place a bromoacetyl moiety in any position along a synthetic peptide chain. The bromo group is displaced by sulfhydryl-containing nucleophiles to give a stable thioether linkage. Synthetic peptide polymers with linkages from head-to-head, head-to-tail and tail-to-tail were prepared using this approach. These polymers are under being study for their immunogenic properties in rabbits.